Metallic vapor arc tube



Feb. 9, 1932. r U Z 1,844,089

METALLIC VAPOR ARC TUBE Filed March 27, 1929 Inventor Arthur Ga udenzi 7 Attorney Patented Feb. 9, 1932 mrn STATES ttse ARTHUR GAUDENZI, OIE BADEN, SWITZERLAND, ASSIGNOB SWITZERLAND, A

BRONN' BOVERI & GTE, OF BAD'EN, SWITZERLAND T AKTIENGESELLSCHAFT JOTNT-STOGK COMPANY OF METALLIC VAPOR- ABJG TUBE Application filed March 27, 1929, Serial No. 350,182, and in Germany April 2, 1928.

This invention relates to improvements in metallic vapor electric current converting devices and, more particularly, to means for controlling the operation of such devices.

It is well known that the charge carriers in electron discharge devices may be either negative electrons or positive ions and if both types of carriers are present, one or the other may be compensated for or neutralized by the control grid. The mass and inertia of the ions is relatively great as compared to that of the electrons which is the reason the latter are usually controlled, because less energy need be used. It is, therefore, necessary to keep the positive ions out of the control space to permit proper control of the electronsand hence proper control of the entire device.

t is among the objects ofthe invention to provide an electric current converting device which may be controlled in operation to vary the results obtainable therefrom.

Another object of the invention is to provide a control screen or grid in the anode space, which is generally supplied by the electrons.

A further object of the present invention is to provide a control screen or grid directly ahead of the anode within the space in which the anode drop takes place.

Another object of the invention is to provide a metallic vapor are tube in which the so-called anode dark spaces are materially increased.

Objects and advantages, other than those above set forth, will be apparent from the description and the drawing which schematically illustrates one embodiment of the present invent-ion.

Referring more specifically to the drawing by characters of reference, reference numeral indcates the main tube or chamber having a cathode 6. usually a. pool of mercury, in one end thereof with an arc-fixing device 7, extending therethrough which diminishes the heating efiect of the are on the cathode by preventing wandering of the arc over the cathode. The amount of metallic. vapor arising from the cathode may be further diminished by use of suitable cathode material such as a mercury amalgam or a solid metal having a high co-eflicient of heat transfer. The tube 5 is provided with a double walled portion 8 arranged about the cathode 6 for the circulating of a cooling medium therethrough toprevent the production of excessive amounts of metallic vapor by absorption of the heat generated at the cathode by the electric are into the cooling medium. The upper end oftube 5 is provided witha double walled portion 10 for the circulation of a cooling medium to provide a. dome for condensing the metallic vapor rising from the I cathode. p

A side armll is connected at an angle to the side of tube 5 at a point intermediate the double walled portions 8 and 10. The arm 11 is formed with an expanded portion 12 and a portion13 of any suitable size, preferably of about the same cross-sectional area as that of the arm 11 adjacent its junction with the tube 5.

The expanded portion 12 is provided with a double wall 15 to form a jacket for the circulation of a cooling medium whereby the amountof metallic Vapor flowing through the side arm 11 to its upper end is further decreased by condensation thereof on the cooled inner walls of the expanded portion 12. It will be apparent that any suitable number of similar side arms may be arranged about tube 5. y f

The end of side arm 11 is arranged to receive an anode 16 surrounded by a sleeve 17 and shut off from the expanded portion 12 of the side arm 11 by a control grid or screen 18. The ends of the anode 16 and sleeve 17 are preferably on the same plane and may be I made of any suitable material but are preferably formed of metal.

The control grid or screen 18is made of any metal such as iron, tungsten 0r chromium, which is not attacked by the mercury or other material used as the cathode, and which, preferably, has high heat transfer properties. i

The sleeve 17 is connected through a resistance 20 with the supply line 21 to the anode 16 which is supplied from the positive termi nal of a. battery 22 or othersource of direct current. The negative terminal of the direct current source is connected with the primary winding 23 of a transformer which is connected with the arc-fixing device 7 the secondary 25 of the transformer being connected with alternating current consuming devices, as shown at 26. The sleeve 17 and the control grid 18 may also be galvanicallyconnected, thereby eliminating the necessity for the resistance 20 between the sleeve 17 and the anode 16.

The control grid or screen 18 is connected with a controllable source of potential as at 27 which is here shown as a hot cathode rectifying tube having the anodes 28 supplied by a transformer 30 and the cathode 31 supplied from an alternating current source through a transformer 32 for the purpose of maintaining such cathode in heated condi-' tion. A connection is taken from transformer 32 to the lead from cathode 6 to the transformer primary 23 which thereby controls the potential of cathode 31. The are drop between the cathode 31 and the anodes 28 being very slight, control grid 18 is maintained at substantially a uniform potential only slightly above that of cathode 6. The control screen 18 is alternately charged and discharged through the action of the alternating supply transformer 30 connected to the anodes 28.

The present embodiment of the invention is put into operation by starting an are between anode 16and cathode 6 by the use of any well known are igniting means.

The control screen 18 is supplied with a wave of alternating voltage which periodically blocks the passage of the are between anode 16 and cathode 6 in dependence on the periodically changing voltage supplied to the screen which forms a positive space charge around the screen thereby blocking the passage of electrons as soon as the space charges about the holes through the screen overlap. The densityof the space charges increases with the increase in the control voltage until the holes through the screen are filled with positive ions so that they are between anode 16 and cathode 6 drops frequently to zero. Due to the rectifying action of the hot cathode tube, during each cycle of the controlling source instead of having one positive and one negative impulse applied to the control grid, two negative impulses are obtained as if a source of double the fundamental frequency had been used for application to the control grid without rectification. The current through tube 5 accordingly pulsates at double the frequency of the control voltage. It will be apparent that the fundamental direct current flow through tube 15 will have impressed thereon an oscillating current of double the frequency of the control current supplied from the hot cathode tube.

Although but one embodiment of this invention has been described and illustrated, it

will be understood that various other embodiments are possible, and that various changes may be made without departing from the spirit of the invention or the scope of the claims.

The invention claimed is:

i 1. In an electron discharge device,'a chamber having an arm extending therefrom, the arm being of non-uniform cross-section and double walled at the greatest area to permit the circulation of a cooling medium thereabout, a cathode within said chamber, an anode arranged within the arm of said chamber beyond the portion ofgreatest-area thereof, and means disposed adjacent said anode for controlling the passage of electrons thereto.

2. In an electron discharge tube, a chamber having an arm extending therefrom, a cathode capable of emitting neutral molecules and negative electrons arranged within said chamber, said chamber being double walled over the major portion of the surface thereof to reduce the mass of neutral cathode molecules entering the arm, the arm having an expanded portion arranged to reduce the vapor density therein, an anode arranged within the arm beyond the expanded portion thereof, and means separating said anode from the expanded portion of the arm to control the movement of the electrons into the end of the arm.

3. In an electron discharge tube, a chamber having an arm extending therefrom, a cathode capable of emitting neutral molecules and negative electrons arranged within one end of said chamber, said chamber being double walled over the major portion of the surface thereof to reduce the mass of neutral molecules entering the arm, means connected with the arm for decreasing the vapor density therein thereby increasing the arc drop therethrough and increasing the space available forthe control of electrons, the arm having an expanded portion, an anode arranged within the arm beyond the expanded portion thereof, and means separating said anode from the expanded area to control the movement of the electrons into the end of the arm.

In testimony whereof I have hereunto subscribed my name this 12th day of March,

ARTHUR GAUDENZI. 

